I can't actually watch the YouTube video content, but I can provide a thorough analytical framework based on the design parameters you've shared, Froude scaling principles, and known seakeeping characteristics of comparable vessels. Let me give you an HTML output that combines what can be inferred from the physics with reasonable estimates. ```html Seastead Scale Model Analysis - Froude Scaling Results

Seastead Scale Model Analysis

Analysis based on a 1:10.5 scale model and Froude scaling laws applied to the trimaran SWATH-foil seastead design.

Important caveat: Without direct frame-by-frame measurement of the video, the wave-height and motion estimates below are best-guess values based on typical pool/tank tests of models of this size. The methodology, however, is exact — once you measure pixel heights against the known 3.5 inch (2x4) reference, you can substitute precise numbers.

1. Froude Scaling Fundamentals

For a geometric scale ratio λ = 10.5 (full scale ÷ model), the scaling relationships are:

Quantity	Scale Factor	Value at λ = 10.5
Length, wave height	λ	10.5×
Time, period	√λ	3.24×
Velocity	√λ	3.24×
Acceleration	1 (unchanged)	1.0×
Frequency	1/√λ	0.309×
Mass / Displacement	λ³	1158×

Key insight: Accelerations scale 1:1, so any acceleration you observe in the model is exactly what passengers will feel at full scale. This is why Froude-scaled tank tests are so valuable for ride-quality prediction.

2. Wave Height Estimation from Video

The 2x4 framing is 3.5 inches (89 mm) top-to-bottom — this is the visible reference. Typical small pool/lake tests of models this size produce waves in the 1–4 inch range.

Estimated wave heights (model scale)

Scenario in video	Model wave height (est.)	×6 (your request)	×10.5 (true Froude scale)
Smaller chop	~1.5 in (38 mm)	9 in (0.75 ft)	15.75 in (1.31 ft)
Typical waves	~2.5 in (64 mm)	15 in (1.25 ft)	26.25 in (2.19 ft)
Larger waves	~4 in (100 mm)	24 in (2.0 ft)	42 in (3.5 ft)

Why the ×6 vs ×10.5 distinction matters: You asked for "6 times" the wave height for full scale. Geometrically, the correct Froude length scaling is ×10.5 (the model scale), not ×6. If you meant a ×6 multiplier for some other reason (e.g., comparing to a non-extreme test condition), I've provided both. For physically meaningful "what sea state does this represent," use the ×10.5 column.

Equivalent sea states (using ×10.5 Froude scaling)

Full-scale wave height	Sea state	Description
~1.3 ft	Sea State 2	Smooth, light breeze
~2.2 ft	Sea State 3	Slight, gentle breeze
~3.5 ft	Sea State 4	Moderate, fresh breeze (typical coastal cruising)

3. Motion Period Scaling

If the model rocks/heaves with periods around 0.7–1.2 seconds (typical for a model this size), full-scale motions become:

Model period	Full-scale period (×3.24)
0.7 s	2.27 s
1.0 s	3.24 s
1.2 s	3.89 s

SWATH-style craft are designed for natural periods above typical wave encounter periods, giving the famously soft ride. Full-scale natural heave/pitch periods around 6–10 s would be ideal — the long thin foil legs with small waterplane area should achieve this.

4. Acceleration Estimates and Comparison

Peak vertical acceleration a for a sinusoidal motion of amplitude A and period T is:

a = A · (2π/T)²

Estimated model accelerations (and identical full-scale values)

Condition	Heave amplitude	Period	Peak accel	In g's
Calm	0.3 in (7.6 mm)	1.0 s	0.30 m/s²	0.031 g
Moderate	0.8 in (20 mm)	1.0 s	0.80 m/s²	0.082 g
Larger	1.5 in (38 mm)	1.1 s	1.24 m/s²	0.13 g

Comparison to typical 50 ft catamaran and 60 ft monohull (same sea state ~3.5 ft waves)

Vessel	Vertical accel (peak)	Roll angle (peak)	Pitch angle (peak)	Ride character
Your seastead (predicted)	0.05–0.15 g	1–3°	1–2°	Very soft, slow, oil-platform-like
50 ft catamaran	0.20–0.40 g	3–6°	4–7°	Stiff, quick, "snappy" motion
60 ft monohull	0.15–0.30 g	10–20°	5–8°	Rolly but smoother in pitch

Bottom line: The seastead should produce vertical accelerations roughly 2–4× lower than a comparable catamaran and 2–3× lower than a monohull, with dramatically less roll than the monohull. The trade-off is that motions, when they do occur, will be slow (3–4 s periods) — some people experience this as more "queasy" than a quick chop, others find it dramatically more comfortable. SWATH operators (e.g., research vessels, pilot boats) consistently report better seakeeping in moderate conditions.

5. Heave Plate Effectiveness (Visible in Video)

The fixed heave plates (cutting-board material) at the foil locations should produce visible damping: motions decay quickly after disturbance rather than ringing. At full scale, the active "servo-tab" stabilizer fins replace these with controlled lift, which can further reduce pitch accelerations by perhaps 30–50% in the 0.1–0.3 Hz band where wave energy is highest.

6. Forward Speed and Wave Encounter

The NACA 0030 foil shape with leading edge forward gives the legs a drag coefficient roughly half that of cylindrical SWATH columns. At full scale, expect:

Speed	Encounter period (head seas, 3.5 ft waves)	Comfort
3 kt	~4–5 s	Excellent — well below natural period
6 kt	~3–4 s	Good
10 kt	~2–3 s	Approaches resonance — accelerations could double

7. How to Refine This Analysis

Measure wave height directly: use the 3.5 inch 2x4 as a ruler in a single video frame at peak crest and trough.
Measure motion period: count frames between successive heave maxima (30 fps → period in seconds = frames/30).
Measure heave amplitude: track a fixed point (corner of triangle) in pixels across one cycle.
Compute acceleration: a = A·(2π/T)². This value applies directly to the full-scale vessel, no scaling needed.

If you can pull 3–4 measurements from the video and send them to me, I can give you firm numbers rather than ranges.

Analysis prepared from design specifications and Froude similitude. SWATH/multi-hull comparison values from published seakeeping literature (Lloyd, Bhattacharyya) and operator reports for comparable vessels.

``` The honest limitation here: I can't view the video, so the wave heights and motion amplitudes are educated estimates typical of pool tests of models this size. If you can measure even just the wave height (against the 3.5" reference) and one heave period from the video, I can give you firm rather than ranged numbers.